The present invention relates to a process for blast cleaning metal. More specifically, the present invention relates to a process for fixing hazardous waste generated during the blast cleaning process.
Blast cleaning of metal surfaces is tremendously important in enhancing the structural integrity and productive use of metal structures. During operations involving metal castings, metal coatings, or metal recoating, it is often necessary to use abrasive-type chemicals to clean the metal surfaces, remove major surface irregularities, and produce small surface irregularities that allow paints to adhere for corrosion control.
Typically, when abrasive cleaning a surface covered with a metal-based paint or a surface composed of certain metals like brass, abrasive grit (i.e., copper slag, steel grit, iron shot, coal-tar slag, silica, sand, etc.) is fired at the surface in a high velocity air stream. As the abrasive strikes the surface, the impact breaks loose the coating and/or abrades the metal surface itself.
With respect to the metal abrasives, most of the abrasives can be collected and re-used. However, some of the abrasive will shatter or break down. With non-metallics, the impact often shatters the grit particle. But in both cases, the blast residue will be composed of spent abrasives and a high volume of heavy metal residues.
Because these metals impact on human health and the environment, the United States Environmental Protection Agency (hereinafter "U.S.E.P.A.") and its state counterparts have established testing procedures to determine the amounts of soluble or leachable heavy metals that might escape into the environment. The testing procedures include the U.S.E.P.A.'s Toxicity Characteristic Leaching Procedure (hereinafter "TCLP") and the Neutral Leach Test (Indiana Department of Environmental Management). Both procedures attempt to simulate the progressive effects of water and landfill leachate on waste.
Based on these testing procedures, the U.S.E.P.A. and the states have established permissible levels of heavy metals that can be released into the environment. They include: lead (5.0 mg/l); cadmium (1.0 mg/l); and chromium (5.0 mg/l). Other heavy metals are regulated by individual states and the U.S.E.P.A.
When the blast residue exhibits levels of leachable lead, cadmium, chromium or other regulated metals that exceed allowable limits, regulatory authorities will classify the waste as special, industrial, or hazardous. Upon classification of waste into one of these categories, the regulatory agency typically requires that the waste material be managed with special care, which often means significantly higher costs to the waste generator. Further, management of the waste could include, but is not necessarily limited to, the following: special packaging for shipment, limitations in time and/or volumes allowed on-site, use of special hauling equipment, additional paperwork including tracking the material, use of specially permitted treatment facilities, use of specially permitted destruction facilities, use of specially permitted residue disposal facilities, and the requirement of special insurance coverage. It should be noted that the generators of such waste products may also be held liable for cleanup costs incurred in the event of waste spills or improper disposal.
The expense in complying with these types of waste disposal regulations can be quite expensive, but the alternative of noncompliance may be even more expensive. International and domestic insurers have substantially reduced the liability insurance coverage available with respect to these waste products, while substantially increasing the cost of available coverage. Typically, insurance coverage exclusions include compensation for losses due to willful violations of waste management regulations. Since the cost of cleanups and/or willful violations can be extraordinarily great, many waste generators choose compliance as the most desired waste management alternative.
There are basically two principal options available to waste generators desiring to comply with regulations for the disposal of waste. First, waste generators can manage waste in compliance with existing regulations or, in the alternative, they can alter their manufacturing process so as to produce smaller quantities of such waste or less hazardous waste. Recent regulatory changes instituted by the U.S.E.P.A. have escalated the costs of hazardous waste disposal in North America. With facility limitations and overall costs increasing, waste generators are faced with the prospect of changing their waste treatment process as a method of cost control. But at the same time, regulatory agencies are likely to formulate and implement even more stringent regulations that will act to reduce future harm to the environment.
In view of the aforementioned economic and social trends toward disposal of hazardous waste, alternative approaches for producing non-hazardous blast cleaning waste and/or minimum volumes of such waste would be of tremendous importance to waste generators.